1. Field of the Invention
The present invention relates to an image processing method and device, and more particularly to an image processing method and device for converting multiple-value image data into n-value data (where n is an integer equal to or greater than 2).
2. Description of the Related Art
Known image processing methods for performing gradient representation include the error diffusion method (hereafter referred to as the ED method), the mean density method (hereafter referred to as the MD method) such as disclosed in U.S. Pat. No. 5,121,446 and U.S. Pat. No. 5,577,136, and so forth. These methods attempt macro-representation of gradients by representing area gradients using a few gradients. In other words, these are pseudo gradient representation methods. These methods are advantageous in that the load on the hardware handling the image data can be reduced, owing to the fact that an image can be formed using few gradients.
However, there have been problems in that some printers are not able to accurately output solitary dots from the n-value process, depending on the properties of the printer. Attempting pseudo gradient representation methods with a printer not able to accurately output such solitary dots has resulted in trouble such as irregular concentration at certain concentration ranges or formation of pseudo outlines.
Accordingly, it has been proposed to deal with the problem in such printer properties by concentrating the dots to a certain degree. However, this is a problem, since simply applying high dot concentration to the entire concentration area decreases the overall output resolution of the image.
Another problem is that creating the hardware for concentrating dots for one set of printer properties necessitates reconfiguring or remaking the hardware each time the printer properties change.
There has also been a problem wherein compressing error diffused images using a facsimile or the like yields a small compression rate, since the rate of contact between the white dots and black dots is small.
The present invention has been made in light of the above-described problems in the known art, and accordingly, it is an object of the present invention to provide an image processing method and device capable of controlling the amount of dot concentration at any concentration area.
It is another object of the present invention to provide an image processing method and device capable of controlling dot concentration based on the state of n-value-izing of multi-value image data, preventing deterioration of output resolution which occurs with dot concentration.
It is yet another object of the present invention to enable control of the amount of dot concentration according to printer properties.
It is still another object of the present invention to provide an image processing method and device capable of controlling the amount of dot concentration in certain concentration ranges at which pseudo outlines or irregularities in concentration, for example, tend to occur.
It is a further object of the present invention to enable accurate control of texture by controlling the threshold value of the n-value-izing process according to the array pattern resulting from previous n-value-izing cases. Now, the term xe2x80x9caccurate control of texturexe2x80x9d refers to controlling to a desired dot position when recording.
In order to achieve the above objects, an image processing device according one aspect of the present invention includes:
means for inputting multi-value image data, and means for converting the multi-value image data input by the input means into n-value data.
The device also includes means for controlling the amount of concentration of dots represented by the n-value data obtained by the converting means, and means for judging the concentration of the input image.
The control means controls the amount of concentration of dots according to the concentration of the image judged by the judging means.
Also, in order to achieve the above objects, an image processing device according to another aspect the present invention includes
means for inputting multi-value image data,
means for converting the multi-value image data input by the input means into n-value data, and
means for controlling the amount of concentration of dots represented by the n-value data obtained by the converting means.
The device also includes means for storing the n-value data of a plurality of pixels obtained by the converting means.
The control means controls the amount of concentration of dots based on the n-value data of the plurality of pixels, stored in the storing means.